Punch45 Constant Noise from right channel-?

[Satyr]

Hey all,
I decided to take the plunge and try to repair some of my old car amps (instead of just building speakers from time to time) as hobby projects.

I recently picked up a Punch 45 (HD), and after replacing the junk wire the PO had connected to it (with what looked like telephone crimping stuff) I got it to power on, but I have a high amount of static like crackling noise from the right channel. Initially, I thought it was due to the loose rca inputs- (and there may still be a problem with the inputs) but I tacked them back to their mounting surface (where they had become detatched) with a bit of solder and the noise continues.

I did alot of searching before posting, and found one old, dead, unresolved post where someone had a similar problem with an RF amp, and Perry had asked him to measure the resistance between the input rca shields/sleeves. I checked the resistance between the shields on this P45 and now that they're tacked down, they read 0.6 ohms between them.

So, what would be next?

I thought I would post this as a diy tutorial for others to follow who might be interested, and I will be reading on the bcae site as well. If there are any other sites that might help me repair a RF amp (or any other amps) I'd really appreciate the info. Thanks in advance and have a good week- John

[Perry Babin]

Is there any corrosion between the components on the board just behind the RCA jacks?

[Satyr]

Hi Perry, Thank you very much for responding. No, there isn't any corrosion- in fact, compared to many of the pictures I've seen of damaged amps, this one appears to be in pretty good shape. No burned spots, no broken traces, etc.

[Perry Babin]

If it's noisy. you'll have to trace the signal to see where the noise is getting into the system.

[seankane]

Look on the HBPIM board right behind the RCA jacks and look at the 2 10uf 16v aluminum capacitors and see if there is any brown spots around them.

[dwvinky]

Originally Posted by seankane

Look on the HBPIM board right behind the RCA jacks and look at the 2 10uf 16v aluminum capacitors and see if there is any brown spots around them.

Ive purchased two 75hd's and a 45hd in the past month. All have ruptured caps on the PIM. Boards aint cheap either. Eventually when i quit buying broken amps, i'll order replacements. Lol. First thing im gonna do when i get new boards is replace the aluminum caps with low profile leaded radial caps. Ill just keep the leads short and heat shrink em.

[Satyr]

Hooked it back up to power and realized that the crackling, popping static noise was in both channels- and... whatever was failing, failed. Pop, smoke. Now it's dead...

I didn't have burned spots before, but I do now...

[Satyr]

Very bummed about this- my first project up in smoke (literally.) Would it be OK to try and post a picture of the burned spots for feedback/direction from y'all?

[Perry Babin]

Post the photos.

Were the transistors clamped to the heatsink when it failed?

[Satyr]

[/IMG]

Hope this works. This is a macro of the whole board with purple arrows showing visble burns